It seems that we explicitly disable certain mochitest-chrome tests in dom/plugins/test/mochitest/Makefile.in when there is no crash reporter enabled, but there are also tests in mochitest-plain that require it to be enabled to work properly:
mochitest-plain failed:
74 ERROR TEST-UNEXPECTED-FAIL | /tests/dom/plugins/test/test_crashing.html | This test did not leave any crash dumps behind, but we were expecting some!
372 ERROR TEST-UNEXPECTED-FAIL | /tests/dom/plugins/test/test_hanging.html | This test did not leave any crash dumps behind, but we were expecting some!
This is turning ASan builds orange on mochitest-3 so I would like to fix this by enabling these tests only when the crash reporter is enabled.